Methanol is an important industrial chemical that has many uses including (a) as a fuel or fuel additive, (b) as a raw material for production of chemicals such as formaldehyde and acetic acid, and (c) as an industrial solvent (windshield washer fluid, antifreeze, hydrate inhibitor).
Methanol is produced from a methanol synthesis gas comprised mainly of hydrogen, carbon monoxide and carbon dioxide with essentially no methane. Methanol synthesis proceeds via the following catalytic reactions:CO+2H2↔CH3OHCO2+3H2↔CH3OH+H2O
Side reactions include the formation of dimethyl ether and higher alcohols. The production of methanol is maximized when the module number R defined below is at an optimum value in the range of 2 to 2.1:
  R  =                    H        2            -              CO        2                    CO      +              CO        2            
The feedstock for producing synthesis gas is either natural gas or a solid hydrocarbon such as coal or petroleum coke. In some instances, heavy petroleum liquids such as asphaltenes or biomass have also been used.
The methanol synthesis gas is conventionally generated by one of the following routes: (1) steam reforming of natural gas, (2) autothermal reforming of natural gas and (3) noncatalytic gasification of solid hydrocarbonaceous feedstocks such as coal or petroleum coke with oxygen.
Each of the methods of synthesis gas generation produces synthesis gas having a natural module number that is not close to the optimum value of 2 to 2.1. Steam reforming of natural gas produces a synthesis gas with R=3 to 3.5. This results in an excess of hydrogen that must either be sold as a by-product or combusted as fuel in a fired heater. Autothermal reforming of natural gas with steam and oxygen produces a synthesis gas with R=1.7 to 1.8. This method is closest to being optimal and a viable option since considerable development in autothermal reforming technology and catalysts has taken place. Conventional noncatalytic gasification of coal and petroleum coke produces a synthesis gas with R=0.4 to 0.6. The high operating temperature (2600-2900° F.; about 1427-1593° C.) results in high oxygen consumption and a low R value of less than 1. The large deficiency of hydrogen must be met by subjecting a significant fraction of the synthesis gas to the water-gas shift reaction:CO+H2O↔H2+CO2 
Shifting the gas to increase the module number is undesirable since it lowers the carbon conversion to methanol. Thus, the natural module number of synthesis gas production technologies is either undesirable in terms of hydrogen conversion or in terms of carbon conversion.